IFITM1(Interferon induced transmembrane protein 1) is a small membrane-associated interferon-stimulated gene that modulates innate immune signaling and restricts the entry and replication of diverse enveloped viruses by altering membrane properties and endosomal trafficking. Its expression is induced downstream of type I/II interferon pathways through JAK–STAT signaling and contributes to cellular antiviral state programs and immune–epithelial interactions. IFITM1 also participates in processes linked to cell adhesion, proliferation, and stress responses, connecting interferon signaling to broader transcriptional and membrane remodeling networks. Dysregulated IFITM1 expression has been reported in inflammatory settings and multiple cancer contexts, making it a useful marker and functional node for studies of host–pathogen interactions and tumor-associated interferon responses.